Fillings have long been and likely will continue to be used in restorative dentistry to treat cavities in teeth. After excessive wear, marginal leakage, recurrent caries, a filling may damage, requiring either repair or replacement. However, prior art techniques proposed to repair and replace fillings have been disadvantageous in many respects. To date, the conventional repair or replacement of fillings, especially composite fillings, entail various difficulties.
The loss of tooth structure resulting from dental caries, or tooth decay, is commonly known as a cavity. The formation of a cavity is an invasive process affecting the structure of a tooth. A tooth has several layers. In basic terms, the outermost layer, the enamel, is the hardest and most mineralized substance in the body. Below the gum-line, a substance called cementum covers the tooth roots. Under both the enamel and the cementum is the dentin. The dentin, which is almost as hard as bone, contains nerve endings. Below the dentin is the dental pulp. The dental pulp is a vascular tissue, including capillaries, blood vessels, connective tissue, nerve fibers, and cells, which include odontoblasts, fibroblasts, macrophages, and lymphocytes. The dental pulp nourishes the tooth during development of the tooth.
A cavity is an infection caused by the interaction of dietary carbohydrates and bacteria found in the mouth. Proteins in saliva and food debris are combined with the bacteria to form a film known as plaque. The plaque coats the tooth with the bacteria. The most common forms of bacteria believed to play a role in the formation of cavities include Streptococcus mutans, Lactobacillus casei and acidophilus, and Actinomyces naeslundi. 
These bacteria consume the carbohydrates of food debris, resulting in acid production. Exposure of the tooth to such acid decreases the PH at the tooth surface. The acid dissolves the enamel, initiating the formation of the cavity. As the cavity progresses, it invades the softer dentin directly beneath the enamel. Ultimately, the cavity may encroach on the nerve and blood supply of the tooth contained in the dental pulp.
The formation of a cavity occurs in two primary ways. First, cavities may form through pits and fissures. Pits and fissures are relatively thin areas of enamel that contain recesses that can trap food and plaque, thus allowing the production of acid. The cavities can typically attack a small, focused area at a vulnerable region and then spread widely to invade the underlying dentin. Second, cavities can attack a relatively smooth surface of the tooth, such as the front or back of a tooth, or in between teeth. Over the smooth surface, the thickness of the enamel is usually more uniform, and not reduced as in the case for pits and fissures. The production of acid can create a cavity with a wide area of attack, which converges as it penetrates deeper layers of the tooth.
Once discovered, the decayed, or carious, tooth structure must be removed before the typical placement of a filling in the cavity. Various removal techniques have been proposed and employed. For example, dental caries or decayed tooth structure has traditionally been removed by a dentist using a dental handpiece and a bur (the dental drill). More recent advances in dental technology and equipment presently also allow removal of decayed tooth structure by laser and air abrasion (micro sandblasting). Hand instruments may also be used in conjunction with one of the above methods. The procedure of caries removal first involves identification of the affected portion of the tooth. This may involve visual detection, tactile detection (e.g. with a dental explorer instrument), a dental x-ray, or a combination of the above. After identification, the area of decay may be removed by use of a dental handpiece and the decay is “drilled” out.
Typically it is desirable that only the area of actual decay is removed. Surrounding healthy or undecayed tooth structure would ideally be preserved and not be removed. During the active procedure of caries removal, the continued presence of decayed tooth is usually determined by the visual appearance and/or surface hardness of the affected area as decayed areas are usually stained or discolored and softer than the relatively hard healthy tooth. Hand instruments are sometimes used to aid in detection and removal of caries. Additionally, the caries may also be “blasted” out with a air abrasion unit or “vaporized” with a dental laser.
The problems posed by the formation of cavities in teeth have motivated various restorative measures and technologies in the field of dentistry. One example of such restorative measures is silver fillings, which are sometimes also referred to as amalgams. Upon detection of a cavity appearing on a tooth, a dental professional, usually a dentist, may propose the application of a silver filling. As its name implies, the silver filling is a silver-based material used to fill or close a cavity or hole in an affected tooth. The composition of such silver-based materials is well-known.
Before placement of the silver-based material in the tooth affected by the cavity, the material is in a relatively malleable, putty-like form. The material is then placed in the cavity. The material hardens in the cavity to form a snug fit with the tooth itself. Usually, no adhesive materials are used or needed to further affix the silver filling in the cavity. The restoration serves to fill the defect created in the tooth resulting from the removal of the caries and also prevents further invasion of the caries by bacteria, food impaction, or the like.
In recent years, however, the use of silver fillings in addressing the problems associated with cavities has not been exclusive. Various factors and considerations have prompted the proposal and use of new restorative dental techniques that do not employ the use of silver-based materials as fillings. For example, growing aesthetic sensibilities have likely emphasized some of the limitations of silver fillings. As a result of their composition, silver fillings appear very conspicuously in the teeth of the persons having the restorations. As is well known, silver fillings appear in a person's mouth as dark but lustrous in stark contrast to the otherwise ivory-like background of natural tooth enamel.
As another example, some countries apparently have altogether abandoned the use of silver fillings for cavities. Such abandonment has been, at least in part, due to concern about their safety. Silver fillings typically will contain some amounts of mercury. The presence of mercury in silver fillings is, according to some, the cause of many health-related problems and afflictions for persons having such silver filings. Arguably, no definitive scientific data apparently establishes or dismisses any link between the use of silver fillings and the onset of medical or health problems. Nonetheless, justifiably or not, widespread health concerns have been another factor in the more limited use of silver fillings. The introduction and development of composites, or resins, including composite fillings, as restorative materials, have also led to the diminished use of silver fillings. Composite, resin, or white fillings have been around for about two decades. Composite fillings are typically composed of an organic polymer known as bisphenol-A-glycidyl methacrylate (BIS-GMA), and inorganic particles such as quartz, borosilicate glass, and lithium aluminum silicate.
As popular and effective as composite fillings are compared to silver fillings, both are similar in their susceptibility to possible damage. Both silver fillings and composite fillings alike may require repair, replacement, or restoration after long or excessive wear, failure due to leakage at the margins, recurrent caries, or undue impact. As a result of excessive wear, silver fillings may lose structural strength. Portions of a silver filling, or the entire filling itself, may weaken, loosen, or simply break off after such wear. To remedy such an event, when only a portion of the silver filling has fallen off, the silver filling may be repaired by replacing the portion of the silver filling broken off with a new silver piece. Alternatively, the entire silver filling, even the portion still attached to the tooth, may be intentionally removed by a dental professional and replaced with a new entire silver filling. Similarly, if the silver filling has fallen off entirely from a tooth, a new silver filling may be prepared to simply substitute for the missing silver filling in the tooth.
Composite fillings may also require repair. Typically, when composite fillings have been damaged by excessive wear or impact, the entire composite filling is replaced, even when only a portion of the composite fillings is damaged or broken off. This is true because the bond strength of composite materials is maximized when the composite is bonded to a tooth surface, rather than to the surface of other composite material.
The repair of composite fillings highlights both advantages and disadvantages in the use of composite materials as restorative materials in dentistry. Composite fillings have without question gained popularity, at least in part, due to their aesthetic qualities. Composite fillings, which are designed in varying shades to match the shade of the teeth into which they are placed, reside relatively inconspicuously in teeth. Because they are designed and selected to seamlessly blend into their visual environment, the composite fillings, and their boundaries often cannot be identified by the naked eye of a dental professional. As a result, when circumstances warrant the removal of a composite filling from a tooth, usually as a repair or replacement measure thereto, it can be extremely difficult for a dental professional to do so. First, the composite filling may be difficult to identify or distinguish from the tooth itself. Second, even if it can be generally located, the precise boundary of the composite filling may be difficult to discern from the surface of the tooth. Because of these and other difficulties, undue amounts of time and effort are expended by dental professionals in identifying the precise extent and dimension of the composite filling.
Various problems arise if such burdensome expenditure of time and effort associated with the prior art is not spent. If the composite filling is extracted in haste, in some circumstances, some remnants of the original composite filling may be left within the tooth. The new composite fillings will then be placed in the tooth alongside these remnants, causing poor bonding of the new composite filling with the tooth. The poor bonding may, in turn, invite further future damage or accelerated weary and early failure to the filling and possibly the tooth as well. Additionally, the poor bonding of the composite filling may lead to increased sensitivity of the nerves, staining of the margins, fracturing of the tooth, or the like. In other circumstances, a hasty attempt to remove a damaged composite filling may result in some portion of the healthy tooth being also removed, weakening of the remaining tooth, damage to the pulp, sensitivity, or the like.
The costs of spending substantial time and effort in attempts to identify the composite filling for restorative purposes burden both the dental professional as well as the patient. Filling damage is a widespread phenomenon. As a result, filling repair or replacement may constitute a significant portion of a dental professional's entire practice. The dental professional is therefore burdened by a procedure that impinges on the dental professional's ability to attend to other, and perhaps more, serious dental problems or conditions. Also, the patient may be charged an amount commensurate with the dental professional's efforts in treating composite filling damage. Such charges are inextricably, either directly or indirectly, tied to the time and effort devoted by the dental professional in performing such services. Clearly, the inability to efficiently and precisely locate the composite filling poses distinct drawbacks to both the dental professional and patient at least.